FAIR VALUE DISCLOSURES - Summary of Financial Assets and Liabilities Measure at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Assets
Derivatives	$ 33,286	$ 12,682
Investment securities available-for-sale	2,626,726	1,349,408
Liabilities
Derivatives	33,278	12,687
Fair Value, Measurements, Recurring
Assets
Derivatives	33,806	12,757
Investment securities available-for-sale	2,626,726	1,349,408
Total	2,660,532	1,362,165
Liabilities
Derivatives	33,321	12,755
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 1
Assets
Derivatives	0	0
Investment securities available-for-sale	95	2,969
Total	95	2,969
Liabilities
Derivatives	0	0
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 2
Assets
Derivatives	33,806	12,757
Investment securities available-for-sale	2,626,631	1,346,439
Total	2,660,437	1,359,196
Liabilities
Derivatives	33,321	12,755
Fair Value, Measurements, Recurring \| Fair Value Measurements Using Level 3
Assets
Derivatives	0	0
Investment securities available-for-sale	0	0
Total	0	0
Liabilities
Derivatives	$ 0	$ 0

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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